1. Field of Invention
The present invention relates to an organic light-emitting diode (OLED) and the method for fabricating the same, and particularly to an active matrix organic light-emitting diode (AMOLED) and the method for fabricating the same.
2. Description of the Related Art
An organic light-emitting diode (OLED) is a semiconductor device capable of converting electrical energy into optical energy. Since OLEDs have advantages of high conversion efficiency, no angle of view (AOV) concern, simpler process, low cost, high response rates, broader operation temperature range and full colorization, OLEDs meet the requirements of multi-media age today and are broadly applied in indicator lights, luminance devices of display panels etc.
The earlier generation of OLED display is mainly driven by low-end passive matrix drive. However, the luminance efficiency and the lifetime of a passive driving device are largely declined along with the increase of display size and resolution. Instead, the active matrix OLED display (AMOLED display) featuring high brightness, low electricity-consumption and long lifetime plays an exceptional role in the current development of OLED displays.
An active matrix organic light-emitting diode (AMOLED) is a device using a thin film transistor (TFT) to drive a light emitting diode, wherein each pixel structure thereof includes an organic light-emitting diode (OLED), a switch TFT, a driving TFT, a storage capacitor, a scan line and a data line. The gray-level of an AMOLED pixel structure depends on the data line voltage. When a scan line turns on a switch TFT, the data line voltage drives the gate of the TFT via the switch TFT, so as to drive a required current to the OLED. Depending on a different voltage level, a corresponding different gray-level of display is produced. On the other hand, when the switch TFT is turned on, the storage capacitor begins with a charging action in order to store the input voltage. Therefore, after the switch TFT is turned off, the storage capacitor still remains the input voltage until the next time to turn on the switch TFT. In this way, the driving TFT remains on-state, so that the OLED keeps the original display brightness.
In a typical bottom emitting AMOLED, to keep a required frame quality, the storage capacitor is designed with a sufficient capacitance, and therefore the electrodes of the storage capacitor need to have enough area. However, the electrodes of the storage capacitor and the TFT gate are fabricated by opaque materials, and only an aperture ratio of approximate 30% is given. Thus, when a color filter is integrated into an OLED panel, the luminance brightness of the pixel array of a bottom emitting AMOLED is obviously not as good as a top emitting AMOLED.